In many types of vehicles, both marine craft and land based vehicles, combustion engines are employed as motive power plants. Such engines, in turn, are usually divided into two broad catagories: (a) those in which ignition of the fuel is achieved by use of continuous or timed igniters (spark plugs or the like) and (b) those in which ignition of the fuel is achieved by causing the fuel to reach ignition temperature through sufficiently high compression of the fuel (as in diesel engines). Generally, such engines employ electrically driven engine starter motors for initially cranking and starting the engines after the engines have been shut-down. The energy for driving such starter motors is, in turn, provided from electical storage battery means carried by the respective vehicles. Further, such storage battery means are also usually employed, during engine cranking and starting, as the source of the electrical energy for the associated ignition system. In diesel engine applications, glow plugs are employed for initially creating the ignition of the fuel since, at that time, the rate of heat transfer through the cylinder walls is too great to enable, merely by compression, the development of a temperature of a magnitude sufficient to cause fuel ignition. In such installations, the storage battery means usually provides the electrical energy for heating the glow plugs for engine starting.
Further, in many of such vehicles, electrical generators (some referred to as alternators) are driven by the vehicular engine for both charging the storage battery means and to supply electrical energy to other accessories in and about the vehicle. In many of such arrangements, the output of the electrical generating means decreases significantly at relatively low engine speeds and consequently, as at curb idle engine operation, it is not unusual for such generating means to be incapable of providing all of the electrical energy required by the accessories then in use and, at such time, the remainder of the required or demanded electrical energy is supplied by the storage battery means.
Accordingly, it can be seen that it is very important to maintain the storage battery means charged to a particular potential as to thereby be assured that the storage battery means will have the required energy level when demand is placed thereon. This becomes especially important in winter when very cold ambient temperatures significantly reduce the effectiveness of the storage battery means.
As an attendant consideration, where vehicular engine driven electrical generating means are employed for charging the storage battery means, it becomes important that the generating means actually charge the storage battery means. In this connection, it becomes important that the generating means apply a charging voltage which is sufficiently high and yet not too high since a resulting excessive charging rate can damage both the storage battery means as well as other attendant electrical system components.
The same general problems and considerations also apply to the electrical current in that excessive current as well as insufficient current magnitudes can be either or both an indication of a problem occurring within the circuit in question or the cause of damage to related components and circuitry.
Accordingly, the invention as herein disclosed and described is primarily directed to the sensing of the electrical condition of storage battery means and the output of a generating system as well as other related and attendant problems. However, as will become more apparent, even though the problems described arose in a particular field or art, the invention is not so limited and may be employed in differing fields or arts.